A primary application of optical 3D measurement systems has been in the replacement of mechanical coordinate measurement machines (CMMs). The advantage of optical 3D systems is typically greater speed and flexibility of operation over even the best CMMs. However, the two technologies are not necessarily one to one replacements, requiring new methods of use and in general proof of performance. This paper will present specific data that highlights the differences between CMMs and optical 3D systems and suggests a method to properly achieve CMM compatible results with an optical 3D system and the problems seen in this study.